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Replace data race with use of pthread_once (ftpl_init)

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At the cost of no longer nicely detecting recursive initialisation
problems.

Fixes Debian bug #1093599
This commit is contained in:
Ian Jackson
2025-01-21 18:44:42 +00:00
parent 92c322507c
commit 2503b0fffc
1 changed files with 7 additions and 43 deletions
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50
src/libfaketime.c
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@@ -304,7 +304,7 @@ static bool check_missing_real(const char *name, bool missing)
#define CHECK_MISSING_REAL(name) \
check_missing_real(#name, (NULL == real_##name))
static int initialized = 0;
static pthread_once_t initialized_once_control = PTHREAD_ONCE_INIT;
/* prototypes */
static int fake_gettimeofday(struct timeval *tv);
@@ -2346,44 +2346,12 @@ int clock_gettime(clockid_t clk_id, struct timespec *tp)
#endif
{
int result;
static int recursion_depth = 0;
if (!initialized)
{
recursion_depth++;
#ifdef FAIL_PRE_INIT_CALLS
fprintf(stderr, "libfaketime: clock_gettime() was called before initialization.\n");
fprintf(stderr, "libfaketime: Returning -1 on clock_gettime().\n");
if (tp != NULL)
{
tp->tv_sec = 0;
tp->tv_nsec = 0;
}
return -1;
#else
if (recursion_depth == 2)
{
fprintf(stderr, "libfaketime: Unexpected recursive calls to clock_gettime() without proper initialization. Trying alternative.\n");
DONT_FAKE_TIME(ftpl_init()) ;
}
else if (recursion_depth == 3)
{
fprintf(stderr, "libfaketime: Cannot recover from unexpected recursive calls to clock_gettime().\n");
fprintf(stderr, "libfaketime: Please check whether any other libraries are in use that clash with libfaketime.\n");
fprintf(stderr, "libfaketime: Returning -1 on clock_gettime() to break recursion now... if that does not work, please check other libraries' error handling.\n");
if (tp != NULL)
{
tp->tv_sec = 0;
tp->tv_nsec = 0;
}
return -1;
}
else {
ftpl_init();
}
#endif
recursion_depth--;
}
ftpl_init();
// If ftpl_init ends up recursing, pthread_once will deadlock.
// (Previously we attempted to detect this situation, and bomb out,
// but the approach taken wasn't thread-safe and broke in practice.)
/* sanity check */
if (tp == NULL)
{
@@ -2795,7 +2763,6 @@ static void ftpl_really_init(void)
#undef dlsym
#undef dlvsym
initialized = 1;
#ifdef FAKE_STATELESS
if (0) ft_shm_init();
@@ -3046,10 +3013,7 @@ static void ftpl_really_init(void)
}
inline static void ftpl_init(void) {
if (!initialized)
{
ftpl_really_init();
}
pthread_once(&initialized_once_control, ftpl_really_init);
}
void *ft_dlvsym(void *handle, const char *symbol, const char *version,